Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
9,437
result(s) for
"Singh, R. P."
Sort by:
Determining hotspots of gaseous criteria air pollutants in Delhi airshed and its association with stubble burning
Transboundary pollutant transport is considered as one of the primary factors causing the seasonal air quality deterioration in Delhi, India’s capital. The highest standard deviations exceeding days in winter for NO
2
(7.14–9.63%) and SO
2
(4.04–7.42%) in 2019–2022 underscore the role of meteorological conditions in Delhi's pollution. In contrast, the post-monsoon season shows the highest pollutant exceedance days (4.52–8.00%) for CO due to stubble burning (SB) in Punjab (68,902 fires/year). Despite the government’s assertions of decreasing SB events (14.68%), the city’s CO exceedance days persistently rose by 6.36%. CAMS data is used for assessing contribution hotspots through back-trajectory analysis at multiple heights. An overlap hotspot of 111 sq. km area is identified in the Southeast parts of Punjab that have a higher contribution to the CO levels in Delhi during the post-monsoon season of 2019. Similarly, hotspots are also observed for SO
2
over industrial areas of Punjab during the post-monsoon and pre-monsoon seasons. The same seasons show similar contributing patterns for NO
2
highlighting the influence of consistent emission patterns and meteorological conditions. The clear delineation of hotspots using the receptor model at multiple heights coupled with source apportionment studies will assist decision-makers in addressing the pollution sources outside Delhi.
Journal Article
Modulation of nitrogen metabolising enzymes and the photosynthetic pigments in wheat upon exogenous application of marigold leachates
Laboratory and pot experiments were conducted to evaluate the influence of leachates of fresh/dry parts of marigold on photosynthetic pigments and nitrogen metabolism of wheat. Considerable decline in chlorophylls and carotenoids and the activities of enzymes of nitrogen metabolism (nitrate reductase, alanine and aspartate aminotransferases, glutamate dehydrogenase and glutamate synthase) was noticed in plants treated with higher concentration of fresh (30% w/v) or dry (10% w/v) leaf and flower leachates of marigold. However, treatment of lower concentrations i.e., 5% (w/v) of leachates of fresh parts and 1% (w/v) leachates of dry parts imparted stimulatory effects. Sodium and potassium contents in different parts of wheat plants showed a significant increase with the increase in the concentration of dry leachates both at pre-flowering and flowering stages. On the other hand, nitrogen and calcium content exhibited a decline with the increase in concentration of leachates. The study indicates that identification of allelochemicals in these leachates may probably help evaluation of marigold as a natural herbicide for sustainable agriculture paving way for further study.
Journal Article
Race non-specific resistance to rust diseases in CIMMYT spring wheats
Rust diseases continue to cause significant losses to wheat production worldwide. Although the life of effective race-specific resistance genes can be prolonged by using gene combinations, an alternative approach is to deploy varieties that posses adult plant resistance (APR) based on combinations of minor, slow rusting genes. When present alone, APR genes do not confer adequate resistance especially under high disease pressure; however, combinations of 4–5 such genes usually result in “near-immunity” or a high level of resistance. Although high diversity for APR occurs for all three rusts in improved germplasm, relatively few genes are characterized in detail. Breeding for APR to leaf rust and stripe rust in CIMMYT spring wheats was initiated in the early 1970s by crossing slow rusting parents that lacked effective race-specific resistance genes to prevalent pathogen populations and selecting plants in segregating populations under high disease pressure in field nurseries. Consequently most of the wheat germplasm distributed worldwide now possesses near-immunity or adequate levels of resistance. Some semidwarf wheats such as Kingbird, Pavon 76, Kiritati and Parula show high levels of APR to stem rust race Ug99 and its derivatives based on the
Sr2
-complex, or a combination of
Sr2
with other uncharacterized slow rusting genes. These parents are being utilized in our crossing program and a Mexico-Kenya shuttle breeding scheme is used for selecting resistance to Ug99. High frequencies of lines with near-immunity to moderate levels of resistance are now emerging from these activities. After further yield trials and quality assessments these lines will be distributed internationally through the CIMMYT nursery system.
Journal Article
Climatological aspects of the optical properties of fine/coarse mode aerosol mixtures
Aerosol mixtures composed of coarse mode desert dust combined with fine mode combustion generated aerosols (from fossil fuel and biomass burning sources) were investigated at three locations that are in and/or downwind of major global aerosol emission source regions. Multiyear monitoring data at Aerosol Robotic Network sites in Beijing (central eastern China), Kanpur (Indo-Gangetic Plain, northern India), and Ilorin (Nigeria, Sudanian zone of West Africa) were utilized to study the climatological characteristics of aerosol optical properties. Multiyear climatological averages of spectral single scattering albedo (SSA) versus fine mode fraction (FMF) of aerosol optical depth at 675 nm at all three sites exhibited relatively linear trends up to 50% FMF. This suggests the possibility that external linear mixing of both fine and coarse mode components (weighted by FMF) dominates the SSA variation, where the SSA of each component remains relatively constant for this range of FMF only. However, it is likely that a combination of other factors is also involved in determining the dynamics of SSA as a function of FMF, such as fine mode particles adhering to coarse mode dust. The spectral variation of the climatological averaged aerosol absorption optical depth (AAOD) was nearly linear in logarithmic coordinates over the wavelength range of 440-870 nm for both the Kanpur and Ilorin sites. However, at two sites in China (Beijing and Xianghe), a distinct nonlinearity in spectral AAOD in logarithmic space was observed, suggesting the possibility of anomalously strong absorption in coarse mode aerosols increasing the 870 nm AAOD.
Journal Article
Impact of anthropogenic disturbance and climate on bamboo distribution in shifting cultivation landscapes of Northeast India
Bamboo, a multipurpose plant species found in tropical and subtropical regions, covers about 1% of the earth’s landmass and provides numerous ecosystem services. This study focuses on mapping the distribution of bamboo in the Dima Hasao district of Assam, India, and examines the influence of anthropogenic disturbance and climate on bamboo occurrence in shifting cultivation landscapes. Bamboo distribution was mapped using spectral and textural variables from Sentinel-2 imagery (March and November 2022) and topographic data from the Shuttle Radar Topography Mission digital elevation model. Three machine learning classifiers, random forest (RF), support vector machine, and artificial neural network, were evaluated for bamboo classification. Among these, the RF classifier achieved the highest performance, with an overall accuracy of 87.54%, a producer’s accuracy of 86.86%, and a user’s accuracy of 83.35% when using the combination of March and November median imagery. The short-wave infra red (SWIR) bands were found to be important variables for land use land cover classification, while the normalized difference vegetation index based on the vegetation red edge 2 band (NDVIre2) emerged as the most significant variable for bamboo mapping. A disturbance map for bamboo growing areas was also generated using LandTrendr in Google Earth Engine based on the normalized burn ratio (NBR) from time-series Landsat data and validated using TimeSync. The results indicated that approximately 78.9% of bamboo-growing areas in the district had undergone high disturbance, largely attributed to frequent practice of shifting cultivation. The influence of climatic drivers on bamboo distribution was analyzed using the RF algorithm, and vapour pressure deficit was identified as the most influential factor. This first-of-its-kind study in Northeast India offers key insights into bamboo ecology and demonstrates the value of advanced classifiers in improving distribution accuracy. The study has important implications for forest policy and landscape management in shifting cultivation regions, providing a foundation for conservation planning, climate adaptation, and contributions to climate resilience and relevant UN Sustainable Development Goals.
Journal Article
Global status of wheat leaf rust caused by Puccinia triticina
Leaf rust caused by Puccinia triticina is the most common and widely distributed of the three wheat rusts. Losses from leaf rust are usually less damaging than those from stem rust and stripe rust, but leaf rust causes greater annual losses due to its more frequent and widespread occurrence. Yield losses from leaf rust are mostly due to reductions in kernel weight. Many laboratories worldwide conduct leaf rust surveys and virulence analyses. Most currently important races (pathotypes) have either evolved through mutations in existing populations or migrated from other, often unknown, areas. Several leaf rust resistance genes are cataloged, and high levels of slow rusting adult plant resistance are available in high yielding CIMMYT wheats. This paper summarizes the importance of leaf rust in the main wheat production areas as reflected by yield losses, the complexity of virulence variation in pathogen populations, the role cultivars with race-specific resistance play in pathogen evolution, and the control measures currently practiced in various regions of the world.
Journal Article
Quantitative trait loci of stripe rust resistance in wheat
KEY MESSAGE : Over 140 QTLs for resistance to stripe rust in wheat have been published and through mapping flanking markers on consensus maps, 49 chromosomal regions are identified. Over thirty publications during the last 10 years have identified more than 140 QTLs for stripe rust resistance in wheat. It is likely that many of these QTLs are identical genes that have been spread through plant breeding into diverse backgrounds through phenotypic selection under stripe rust epidemics. Allelism testing can be used to differentiate genes in similar locations but in different genetic backgrounds; however, this is problematic for QTL studies where multiple loci segregate from any one parent. This review utilizes consensus maps to illustrate important genomic regions that have had effects against stripe rust in wheat, and although this methodology cannot distinguish alleles from closely linked genes, it does highlight the extent of genetic diversity for this trait and identifies the most valuable loci and the parents possessing them for utilization in breeding programs. With the advent of cheaper, high throughput genotyping technologies, it is envisioned that there will be many more publications in the near future describing ever more QTLs. This review sets the scene for the coming influx of data and will quickly enable researchers to identify new loci in their given populations.
Journal Article
Selective tuning of Hilbert spaces in states encoded with spatial modes of light
Spatial modes of light directly give the most easily accessible degree of freedom that span an infinite dimensional Hilbert space. The higher dimensional spatial mode entanglement realized using spontaneous parametric down conversion (SPDC) process is generally restricted to the subspace defined by a single spatial mode in pump. Access to other modal subspaces can be realized by pumping beams carrying several easily tunable transverse modes. As a proof of principle experiment, we generate twin-photon states in an SPDC process with pump as a superposition of first order Laguerre-Gaussian (or Hermite-Gaussian) modes. We show that the generated states can be easily tuned between different subspaces by controlling the respective modal content in the pump superposition.
Journal Article
Synoptic weather conditions and aerosol episodes over Indo-Gangetic Plains, India
The present study focuses on identifying the main atmospheric circulation characteristics associated with aerosol episodes (AEs) over Kanpur, India during the period 2001–2010. In this respect, mean sea level pressure (MSLP) and geopotential height of 700 hPa (Z700) data obtained from the NCEP/NCAR Reanalysis Project were used along with daily Terra-MODIS AOD₅₅₀ data. The analysis identifies 277 AEs [AOD₅₀₀ > [Formula: see text] ₅₀₀ + 1STDEV (standard deviation)] over Kanpur corresponding to 13.2 % of the available AERONET dataset, which are seasonally distributed as 12.5, 9.1, 14.7 and 18.6 % for winter (Dec–Feb), pre-monsoon (Mar–May), monsoon (Jun–Sep) and post-monsoon (Oct–Nov), respectively. The post-monsoon and winter AEs are mostly related to anthropogenic emissions, in contrast to pre-monsoon and monsoon episodes when a significant component of dust is found. The multivariate statistical methods Factor and Cluster Analysis are applied on the dataset of the AEs days’ Z700 patterns over south Asia, to group them into discrete clusters. Six clusters are identified and for each of them the composite means for MSLP and Z700 as well as their anomalies from the mean 1981–2010 climatology are studied. Furthermore, the spatial distribution of Terra-MODIS AOD₅₅₀ over Indian sub-continent is examined to identify aerosol hot-spot areas for each cluster, while the SPRINTARS model simulations reveal incapability in reproducing the large anthropogenic AOD, suggesting need of further improvement in model emission inventories. This work is the first performed over India aiming to analyze and group the atmospheric circulation patterns associated with AEs over Indo-Gangetic Plains and to explore the influence of meteorology on the accumulation of aerosols.
Journal Article